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Refined theory of two‐photon processes accounting for virtual electric quadrupole and magnetic dipole transitions
Author(s) -
Egorova N.,
Kouzov A.,
Chrysos M.,
Rachet F.
Publication year - 2005
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1284
Subject(s) - dipole , quadrupole , raman scattering , magnetic dipole , electric dipole transition , atomic physics , polarization density , x ray raman scattering , physics , scattering , chemistry , polarization (electrochemistry) , excitation , raman spectroscopy , molecular physics , optics , magnetic field , magnetization , quantum mechanics
Two‐photon transition amplitudes, accounting for virtual double electric dipole–electric quadrupole ( E 1, E 2) and electric dipole–magnetic dipole ( E 1, M 1) transitions, are derived for isotropic molecular ensembles. The new‐type non‐resonant Raman scattering is shown to appear from the interfering emission fields generated by multipoles (electric dipole, electric quadrupole and magnetic dipole) induced on a scattering particle. The interference is found to affect strongly the angular distribution and polarization characteristics of the scattered radiation, damping the forward scattering while enhancing the backward scattering. When the excitation frequency approaches an absorption resonance, the interference features are shown to disappear from the Raman spectra. In the off‐resonance case, the Raman cross‐section equations for gases of linear and spherical ( T d ) molecules are elaborated in terms of the mixed electronic polarizabilities expressed via their invariants in the molecule‐fixed frame. Copyright © 2005 John Wiley & Sons, Ltd.